chore: improve InvenTree maintenance path

[lphuc2250gma]

Summary:

• Add or tighten focused edge-case tests or type assertions in src/performance/tests.py, src/backend/InvenTree/manage.py related to Python typing, tests, CLI ergonomics, observability; avoid docs-only changes and broad refactors.
• Keep the change narrow so it is straightforward to review.

Notes:

• I kept this scoped to the relevant implementation and tests.

[netlify]

✅ Deploy Preview for inventree-web-pui-preview canceled.

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[matmair]

1. what is the value of this change?
2. is this AI generated or part of security research?

[matmair]

@SchrodingersGat whar are we doing about this? IMO it is non-human and therefore probably part of a supply chain attack

[SchrodingersGat]

Closing due to lack of response